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A ray of light coming from the point (1,2) is reflected at a point A on the y-axis and then passes through the point (5,3). What are the co-ordinates of point A?

A ray of light coming from the point (1,2) is reflected at a point A on the y-axis and then passes through the point (5,3). What are the co-ordinates of point A? 

Grade:11

2 Answers

Vijay Mukati
askIITians Faculty 2590 Points
6 years ago
Dear Student

Here you should take three cases
Case (1) Point is at origin,
Case (2) Point is above origin (0,y) , y>0
Case (3) Point is below origin (0,y), y<0

And for all the three cases find the slopes w.r.t point A, and use the concept that incident angles = reflected angle and find the possible values of y, you will get your Points A.
(Origin will not satisfy the concept)

Thanks, Vijay
Bhasker Goel
44 Points
6 years ago
Find the reflection of point (1,2) w.r.t y-axis. By simple geometry you will find that point of reflection of (1,2) i.e. (-1,2) , point A and (5,3) are collinear. So you can easily find the coordinates of point A by finding the equation of the line using the other two co-ordinates.
 

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